1. Field of the Invention
The present invention relates, in general, to projecting or displaying video/animated or still three dimensional (3D) images, and, more particularly, to autostereoscopy and autostereoscopic projection systems such as those adapted to display ghost or latent 3D images without requiring accurate tracking of a viewer's right and left eye or glasses, headgear, or other equipment that has to be worn or used by a viewer.
2. Relevant Background
There are numerous entertainment and other settings where it is desirable to create a unique visual display. For example, theme or amusement parks may include rides or walk-through attractions where guests (or “viewers”) are entertained by a unique visual effect or illusion. Pepper's ghost is an illusionary technique used by magicians, by ride or attraction designers, and others to produce a 3D illusion of a latent or ghost-like image. Using a simple piece of plate glass and special lighting techniques, Pepper's ghost systems can make objects appear and disappear within a scene or room. Generally, these systems include a main room or scene that is readily viewed by a guest or viewer and a hidden room that is not visible to the viewer, and both rooms may be identical in their physical structure including furniture and other objects except the hidden room may include additional objects or characters such as a ghost. A large piece of glass or a half-silvered mirror is situated between the viewer and the scene at an angle such as about 45 degrees. When the main room is lit and the hidden room is darkened, the viewer only sees the main room as the hidden room does not reflect from the glass, which is itself hard to see as it typically extends across the entire view of the main room. However, Pepper's ghost becomes very visible to the viewer when the entire hidden room or portions such as the ghost or other character are brightly lit. Since only a portion of the light cast upon the ghost or other objects in the hidden room is reflected from the glass, the reflected images appear as latent or ghostly images relative to the objects in the main room (e.g., the reflected images or images superimposed in the visible room may appear to float). The Pepper's ghost image is a 3D image that may be still or animation may be provided such as with animatronics or by placing a live actor in the hidden room.
In a broad sense, the Pepper's ghost systems may be thought of as implementing autostereoscopy, which is generally a method of displaying 3D images that can be viewed without the use of headgear or glasses on the part of the user. In many implementations, autostereoscopy is used to produce depth perception in the viewer even though the image may be produced by a flat device. For example, autostereoscopic or 3D displays may provide flat-panel display systems by using lenticular lenses or a parallax barrier. If a viewer positions his head in particular viewing positions, he perceives a different image with each eye, e.g., a right eye image and a left eye image that produces a stereo image. These displays may have multiple viewing zones allowing multiple users to view the image at the same time. These 3D display systems often have suffered from low resolution, small image size, and varying brightness as the viewer moves his head.
In some 3D projection technologies, it is essential that the left and right eyes of the viewer see only the respective left and right images of the stereoscopic image. To this end, a video is created with cameras set apart by a predefined interoccular distance (i.e., spacing between a human's right and left eye which may be about 2 to 3 inches). So, in these systems, the viewer must be positioned carefully in a known position with their right and left eyes in a particular location to receive the right and left eye images. In an attempt to allow a viewer to move while viewing 3D images, some autostereoscopic projection systems have provided various ways of maintaining the location of the display at the location of the viewer's eyes. For example, much work has been done to create techniques for tracking the location of the viewer's eyes and moving the display in response to project the left and right images to the corresponding viewer eye locations. Other techniques have required that the viewer wear headgear or eyewear that facilitates such tracking. Existing autostereocopic techniques generally teach that the 3D illusion will fail if the images are not projected at the average interoccular distance or if the proper image is not provided to the proper eye of the viewer (e.g., right eye image to viewer's right eye and left eye image to viewer's left eye)
Hence, there remains a need for improved visual display techniques and systems such as for creating or projecting 3D images. Preferably, such methods and systems would be relatively simple to implement, would not require a viewer to wear glasses or headgear, and would be useful in numerous applications including the entertainment industry (e.g., to create 3D illusions for theme parks and other settings).